Shaping Tool and Methods of Using the Same

ABSTRACT

Disclosed are a shaping tool and a method of using the shaping tool, capable of applying a sufficient compressive stress to a shaping member to prevent an excessively high tensile stress from being imposed on the shaping member so as to achieve an extended usable life even if the shaping member is made of a hard and brittle material. The shaping tool comprises a shaping member, a pressure-applying member surroundingly fitted onto the shaping member, a collet chuck surroundingly fitted onto the pressure-applying member, and a casing surroundingly fitted onto the collet chuck. The pressure-applying member has a plurality of outer peripheral slits and a plurality of inner peripheral slits, which are circumferentially arranged in alternate relation and at even intervals. The collet chuck has an externally-threaded portion at an upper or lower end thereof, and a taper surface formed in an outer peripheral surface thereof to have a diameter which gradually decreases toward the externally-threaded portion. The casing has an inner peripheral surface formed as a taper surface in surface contact with the taper surface. The collet chuck is adapted to be reduced in diameter by fastening a nut disposed above or below the casing to the externally-threaded portion, so as to apply a compressive stress to the shaping member.

TECHNICAL FIELD

The present invention relates to a shaping tool, such as a punch or a die, for use in an apparatus for press working, hot/cold forging workings or the like, which is used under high pressures and required to have wear resistance and strong clamping force.

BACKGROUND ART

In a shaping tool for forming a metal material into a predetermined shape through pressing, such as press working or forging working, a high internal pressure applied during the pressing generates a tensile stress in a circumferential direction of the shaping tool, and the shaping tool will be broken if the internal pressure exceeds a material strength thereof. With a view to preventing such fracture or deformation of a shaping tool, the following Patent Publication 1 discloses a structure having a reinforcing ring which is fitted onto an outer peripheral surface of a shaping tool to apply a compressive stress to the shaping tool. In reality, this structure using only the reinforcing ring has difficulty in efficiently applying, to the shaping tool, a compressive stress enough to obtain a sufficient strength of the shaping tool.

The following Patent Publication 2 discloses a method of fabricating a metal electrode through press working using a convex die and a concave die, wherein there is a description about one embodiment where a material having low plastic workability, such as tungsten, is subjected to plastic working based on pressing.

During the plastic working of the material having low plastic workability, a shaping tool, particularly a shaping member having a shaping cavity, is applied with an extremely high pressure, and highly likely to become worn. Thus, the shaping member is required to have wear resistance, and is therefor typically made of a hard and brittle material, such as hard metal.

However, the hard and brittle material inherently has low fracture strength, particularly, to tensile stress, as compared with a ductile material, such as steel, and thereby has poor resistance to a high working pressure. Thus, the shaping member has to be made of a soft ductile material having a relatively high fracture strength, such as HSS (high-speed steel) or tool steel. This causes a problem about severe deformation and wear, and decrease in usable life of the shaping tool.

[Patent Publication 1] JP 2001-138002A

[Patent Publication 2] JP 2003-059445A

DISCLOSURE OF THE INVENTION Problem to be Solved by the Invention

In view of overcoming the problem in the above conventional shaping tool, it is a primary object of the present invention to provide a shaping tool capable of applying a sufficient compressive stress to a shaping member while preventing an excessively high tensile stress from being imposed on the shaping member to eliminate the risk of fracture thereof even if the shaping member is made of a hard and brittle material, so as to achieve a longer usable life of a shaping cavity, and to provide a method of using the shaping tool.

Means for Solving the Problem

In order to achieve the above object, the present invention employs a structure designed to apply a compressive stress to a columnar-shaped shaping member having a shaping cavity on an inward side thereof, during use.

Specifically, according to a first aspect of the present invention, there is provided a shaping tool which comprises a columnar-shaped shaping member having a shaping cavity on an inward side thereof, a ring-shaped pressure-applying member fitted onto an outer peripheral surface of the shaping member in a surrounding manner, a ring-shaped collet chuck fitted onto an outer peripheral surface of the pressure-applying member in a surrounding manner, and a ring-shaped casing fitted onto an outer peripheral surface of the collet chuck in a surrounding manner. The shaping tool is characterized in that: the pressure-applying member has a plurality of outer peripheral slits each formed to penetrate between a top surface and a bottom surface of the pressure-applying member and extend radially in such a manner as to be opened in the outer peripheral surface of the pressure-applying member, and a plurality of inner peripheral slits each formed to penetrate between the top surface and the bottom surface of the pressure-applying member and extend radially in such a manner as to be opened in an inner peripheral surface of the pressure-applying member, wherein the outer peripheral slits are alternately arranged with respect to the inner peripheral slits along a circumferential direction of the pressure-applying member; the collet chuck has an externally-threaded portion at an upper or lower end thereof, and a taper surface formed in the outer peripheral surface thereof to have a diameter which gradually decreases toward the externally-threaded portion; and the casing has an inner peripheral surface formed as a taper surface in surface contact with the taper surface formed in the outer peripheral surface of the collet chuck, wherein the shaping tool includes a nut disposed above or below the casing, and the collet chuck is adapted to be reduced in diameter by fastening the nut to the externally-threaded portion of the collet chuck.

Preferably, in the shaping tool set forth in the first aspect of the present invention, the nut is disposed above or below the casing while interposing a washer therebetween.

In this case, the shaping tool is preferably designed to satisfy the following relations: A1>A2≈A3≈A4 and A5>A2≈A3≈A4, wherein: A1 is a linear thermal expansion coefficient of the pressure-applying member; A2 is a linear thermal expansion coefficient of the collet chuck; A3 is a linear thermal expansion coefficient of the casing; A4 is a linear thermal expansion coefficient of the nut; and A5 is a linear thermal expansion coefficient of the washer.

In the above shaping tool, the nut is first fastened (i.e., rotated in a tightening direction) at room temperature to apply a compressive stress from the collet chuck to the shaping member through the pressure-applying member. Then, when a temperature of the shaping tool is increased, a thermal stress is generated in the pressure-applying member having a relatively high linear thermal expansion coefficient (preferably, having not only a relatively high linear thermal expansion coefficient but also a relatively high Young's modulus), and applied as a compressive stress to the shaping member at a higher value as the casing has a higher Young's modulus (preferably 200 GPa or more). Additionally, when a linear thermal expansion coefficient of the washer is set at a relatively high value, a thermal strain of the washer is applied in a direction for preventing loosening of the nut or in a direction for clamping (i.e., tightening) the collet chuck, so that a high compressive stress never-before possible can be applied to the shaping member. Specifically, a total compressive stress to be applied to the shaping member is “clamping force of the collet chuck at room temperature”+“a thermal stress of the pressure-applying member at an increased temperature”+“additional clamping or anti-loosening of the collet chuck based on thermal expansion of the washer”.

Further, the collet chuck may be made of a material having a moderate Young's modulus (preferably 300 GPa or less), particularly to reduce a tensile stress to be imposed on the casing from the pressure-applying member, so as to prevent fracture of the casing.

As described above, the relation between the respective linear thermal expansion coefficients of the components may be set to be A1>A2≈A3≈A4. In this case, a higher compressive stress is applied to the shaping member as the shaping tool is used at a higher temperature, so that, even if a working pressure is generated during a plastic working, such as a press working, as a source of a tensile stress to be imposed on the entire shaping tool, a compressive stress enough to cancel out the working pressure so as not to cause fracture can be applied to the shaping member. That is, a resulting value of the tensile stress or compressive stress to be imposed on the shaping member becomes equal to or less than a tensile yield strength thereof. Thus, the shaping member can be made of a hard and brittle material without the risk of fracture, to achieve enhanced wear resistance and provide drastically extended usable life to the shaping tool.

In the structure where the nut is fastened through the washer, respective materials of the components may be selected to allow the relation between respective linear thermal expansion coefficients thereof to be set to be A5>A2≈A3≈A4, as described above. In this case, the washer is expanded along with an increase in temperature, to apply a stress to the nut in a direction for pulling the collet chuck, so that the collet chuck is further clamped to apply a compressive force to the shaping member through the pressure-applying member. Even through the operation of fastening the nut at room temperature, a large compressive stress can also be applied to the shaping member through the washer, the collet chuck and the pressure-applying member.

If the pressure-applying member is formed as a solid (i.e., slitless or non-divided) ring-shaped member, an inner diameter thereof becomes larger due to thermal expansion as a working temperature is increased, to cause difficulty in sufficiently applying a compression force to the shaping member. In the shaping tool set forth in the first aspect of the present invention, the pressure-applying member is formed with the outer peripheral slits and the inner peripheral slits which are arranged in circumferentially alternate relation, as described above. Thus, based on synergistic effects of a constraining force of the casing and the inner and outer peripheral slits of the pressure-applying member, a thermal expansion of the pressure-applying member in the circumferential direction thereof along with an increase in working temperature is effectively absorbed and suppressed by the inner and outer peripheral slits, in such a manner that a thermal stress (thermal strain) of the pressure-applying member is transmitted in a direction for compressing the shaping member, i.e., in the radial direction of the pressure-applying member, instead of enlarging respective diameters of the inner and outer peripheral surfaces of the pressure-applying member. This makes it possible to efficiently apply a compressive stress to the shaping member. In this case, with a view to uniformly applying a compressive stress to the shaping member, it is preferable that the outer peripheral slits and the inner peripheral slits are circumferentially arranged in alternate relation and at even intervals, and each of the outer and inner peripheral slits is formed to extend along the radial direction of the pressure-applying member, i.e., to extend in a direction perpendicular to the outer and inner peripheral surfaces of the pressure-applying member.

Instead of forming the inner and outer inner peripheral slits, the pressure-applying member may be divided into a plurality of sub-members in the circumferential direction thereof, in such a manner that the sub-members are disposed in a non-contact relation to each other, to obtain the same effects. That is, the divided sub-members are formed to keep applying a compressive stress to the shaping member without coming into contact with each other, even after they are thermally expanded. In this case, with a view to uniformly applying a compressive stress to the shaping member, the pressure-applying member is preferably divided equally (symmetrically) into a plurality of sub-members in the circumferential direction thereof.

In the shaping tool set forth in the first aspect of the present invention, a bolt may be used in place of the nut. In this case, instead of the aforementioned structure, the casing has an internally-threaded portion in an upper or lower end region of an inner peripheral surface thereof, and a taper surface formed in the inner peripheral surface thereof to have a diameter which gradually increases toward the internally-threaded portion, and the collet chuck has a taper surface formed in the outer peripheral surface thereof to be in surface contact with the taper surface formed in the inner peripheral surface of the casing. Further, the bolt is disposed above or below the collet chuck, and the collet chuck is adapted to be reduced in diameter by fastening the bolt to the internally-threaded portion of the casing. In this case, for the same reasons as those in the aforementioned structure using the nut, the shaping tool is preferably designed to satisfy the following relations: A1>A2≈A3≈A6 and A5>A2≈A3≈A6, wherein: A1 is a linear thermal expansion coefficient of the pressure-applying member; A2 is a linear thermal expansion coefficient of the collet chuck; A3 is a linear thermal expansion coefficient of the casing; A6 is a linear thermal expansion coefficient of the bolt; and A5 is a linear thermal expansion coefficient of the washer. The structure using the bolt has the same effects as those in the structure using the nut.

According to a second aspect of the present invention, there is provided a shaping tool which comprises a columnar-shaped shaping member having a shaping cavity on an inward side thereof, an inner circumferential ring fitted onto an outer peripheral surface of the shaping member in a surrounding manner, and an outer circumferential ring fitted onto an outer peripheral surface of the inner circumferential ring in a surrounding manner. The shaping tool is characterized in that the inner circumferential ring is formed as a pressure-applying mechanism section. Specifically, the shaping tool or the inner circumferential ring (pressure-applying mechanism section) is heated to allow the inner circumferential ring to apply a pressure to the shaping member.

In the shaping tool set forth in the second aspect of the present invention, the pressure-applying mechanism section may have a first structure with a plurality of outer peripheral slits each formed to penetrate between a top surface and a bottom surface of the inner circumferential ring and extend radially in such a manner as to be opened in the outer peripheral surface of the inner circumferential ring, and a plurality of inner peripheral slits each formed to penetrate between the top surface and the bottom surface of the inner circumferential ring and extend radially in such a manner as to be opened in an inner peripheral surface of the inner circumferential ring, wherein the outer peripheral slits are alternately arranged with respect to the inner peripheral slits along a circumferential direction of the inner circumferential ring, or a second structure in which the inner circumferential ring is divided into a plurality of sub-members in a circumferential direction thereof, in such a manner that the sub-members are disposed in a non-contact relation to each other. Preferably, the pressure-applying mechanism section has a linear thermal expansion coefficient equal to or greater than that of the outer circumferential ring. Preferably, the outer circumferential ring has a Young's modulus of 200 GPa or more.

In the shaping tool set forth in the second aspect of the present invention, the inner circumferential ring is formed as the pressure-applying mechanism section having a pressure-applying mechanism adapted to apply a compressive stress to the shaping member in response to heating the shaping tool or the inner circumferential ring (pressure-applying mechanism section). Thus, even if the shaping member is made of a hard and brittle material, the risk of fracture thereof can be eliminate to provide drastically extended usable life of the shaping tool. Preferably, the pressure-applying mechanism section having a linear thermal expansion coefficient equal to or greater than that of the outer circumferential ring is combined with the outer circumferential ring having a Young's modulus of 200 GPa or more. In this case, a stress (thermal stress) due to a thermal strain of the pressure-applying mechanism section can be efficiently transmitted to the shaping member so that the pressure-applying mechanism section can efficiently apply a compressive stress to the shaping member.

As mentioned in connection with the pressure-applying member in the shaping tool set forth in the first aspect of the present invention, if the pressure-applying mechanism section is formed as a solid (i.e., slitless or non-divided) ring-shaped member, an inner diameter thereof becomes larger due to thermal expansion as a temperature of the inner circumferential ring (pressure-applying mechanism section) is increased, to cause difficulty in sufficiently applying a compression force to the shaping member. In the shaping tool set forth in the second aspect of the present invention, the pressure-applying mechanism section is designed to have the pressure-applying mechanism obtained by providing, in inner circumferential ring, the plurality of outer peripheral slits each formed to penetrate between the top surface and the bottom surface of the inner circumferential ring and extend radially in such a manner as to be opened in the outer peripheral surface of the inner circumferential ring, and the plurality of inner peripheral slits each formed to penetrate between the top surface and the bottom surface of the inner circumferential ring and extend radially in such a manner as to be opened in the inner peripheral surface of the inner circumferential ring, wherein the outer peripheral slits are alternately arranged with respect to the inner peripheral slits along a circumferential direction of the inner circumferential ring, or the pressure-applying mechanism obtained by dividing the inner circumferential ring into the plurality of sub-members in the circumferential direction thereof, in such a manner that the sub-members are disposed in a non-contact relation to each other, as described above. This makes it possible to efficiently apply a compressive stress to the shaping member in the same manner as that in the pressure-applying member in the shaping tool set forth in the first aspect of the present invention.

In addition, when a material of the pressure-applying mechanism section is selected to have a linear thermal expansion coefficient equal to or greater than that of the outer circumferential ring, and a Young's modulus of the outer circumferential ring is maximized, a compressive stress to be applied to the shaping member, particularly to the shaping cavity, based on a thermal stress primarily generated by the pressure-applying mechanism section, is further increased to eliminate the risk of dropping-out of the shaping member or deterioration in compressive stress to be applied to the shaping member. In the case where the pressure-applying mechanism section has a linear thermal expansion coefficient equal to that of the outer circumferential ring, even if a temperature is increased, a compressive stress can also be applied to the shaping member to eliminate the risk of dropping-out of the shaping member or deterioration in compressive stress to be applied to the shaping member, because the shaping member is typically made of a hard and brittle material which has a linear thermal expansion coefficient less than those of the pressure-applying mechanism section and the outer circumferential ring. Practically, it is definitely desirable that the pressure-applying mechanism section has a linear thermal expansion coefficient greater that that of the outer circumferential ring.

In the outer circumferential ring having an excessively small Young's modulus, even if the pressure-applying mechanism section is expanded in a heated atmosphere, the outer circumferential ring is concurrently expanded to cause difficulty in efficiently applying a compressive stress to the shaping member. Therefore, it is desirable to maximize the Young's modulus of the outer circumferential ring. Preferably, it is set at 200 GPa or more.

In the above shaping tool of the present invention, even in a situation where the shaping member is made of a hard and brittle material, and the shaping tool is used for a working involving a high tensile stress, such as a plastic working of a material having low plastic workability, such as tungsten, the pressure-applying member can apply a compressive stress to the shaping member while maintaining a tensile stress or compressive stress at a value less than a tensile yield stress of the shaping member. Thus, if a high working pressure is imposed on the shaping member made of a hard and brittle material, the shaping tool can avoid fracture to achieve drastically extended usable life thereof.

Among hard and brittle materials, the shaping member may be made of HSS having high toughness so as to eliminate the risk of fracture of the shaping tool even under use conditions where a high tensile stress is applied thereto. Alternatively, the shaping member may be made of a hard metal having both hardness and toughness so as to obtain enhanced wear resistance and eliminate the risk of fracture of the shaping tool even under use conditions where a tensile stress is applied thereto. Alternatively, the shaping member may be made of a cermet having higher hardness than that of the hard metal even though it is inferior in toughness to the hard metal, so as to obtain higher wear resistance than that of the hard metal. Alternatively, the shaping member may be made of a ceramics having higher hardness than that of the cermet even though it is inferior in toughness to the cermet, so as to obtain higher wear resistance than that of the cermet. Alternatively, the shaping member may be made of a diamond having the highest hardness in natural minerals, so as to obtain high wear resistance, and provide a smooth surface to a shaped product. As to the diamond, a natural diamond, a high-temperature and pressure synthesized diamond, or a sintered diamond subjected to sintering using a metal, such as Co or Ni, as a binder, may be used.

During use of the shaping tool of the present invention, as a working temperature is increased relative to room temperature, the pressure-applying member (or pressure-applying mechanism section) is more largely expanded to apply a higher compressive stress to the shaping member. Thus, the shaping tool of the present invention is suited to a working under high-temperature condition rather than under room-temperature conditions. In fact, while a conventional shaping tool (double shrinkage-fitted module) as shown in FIG. 12 can apply a compressive stress of only about 0.4 GPa to a shaping member at a working temperature of 400° C. if anywhere, the shaping tool of the present invention can apply a compressive stress of about 2 GPa or more to the shaping member.

As above, a larger compressive stress is applied to the shaping member as it is used at a higher temperature. Thus, the shaping tool of the present invention is suited to a plastic working, such as a press working at high temperatures, for obtaining a shaped product using a material having low plastic workability, such as tungsten.

EFFECT OF THE INVENTION

In the shaping tool of the present invention, even under a situation where a high tensile stress is imposed on the shaping member, for example, in a plastic working for a material having low plastic workability, such as tungsten, a high compressive stress can be generally applied to the shaping member to eliminate the risk of fracture of the shaping member even if it is made of a hard and brittle material, and provide drastically extended usable life to the shaping tool. In particular, the shaping member made of a hard and brittle material can have enhanced wear resistance to provide further extended usable life to the shaping tool.

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

FIG. 1 is an exploded perspective view showing a shaping tool according to a first embodiment of the present invention, and FIG. 2 is a sectional perspective view showing the shaping tool in an assembled state. FIG. 3 is a top plan view of a pressure-applying member which is one component of the shaping tool.

The shaping tool illustrated in FIGS. 1 to 3 comprises a shaping member 1, a pressure-applying member 2, a collet chuck 3, a casing 4, a washer 5, a nut 6 and a shim 7.

The shaping member 1 is provided with a shaping cavity 1 a on an inward side of an upper end thereof. The pressure-applying member 2 is formed in a ring shape, and fitted onto an outer peripheral surface of the shaping member 1 in a surrounding manner. As shown in FIG. 3, the pressure-applying member 2 is provided with a plurality of outer peripheral slits 2 a and a plurality of inner peripheral slits 2 b, which are alternately arranged with respect to each other at even intervals in a circumferential direction of the pressure-applying member 2 (i.e., circumferentially arranged in alternate relation and at even intervals). Each of the outer peripheral slits 2 a is formed to penetrate between a top surface and a bottom surface of the pressure-applying member 2 and extend radially in such a manner as to be opened only in an outer peripheral surface of the pressure-applying member 2. Each of the inner peripheral slits 2 b is formed to penetrate between the top surface and the bottom surface of the pressure-applying member, 2 and extend radially in such a manner as to be opened only in an inner peripheral surface of the pressure-applying member 2.

The shaping member 1 and the pressure-applying member 2 is mounted on the shim 7. The collet chuck 3 is formed in a ring shape, and fitted on the outer peripheral surface of the pressure-applying member 2 in a surrounding manner. The collet chuck 3 has an externally-threaded portion 3 a formed at a lower end thereof, and a taper surface 3 b formed in an outer peripheral surface thereof to have a diameter which gradually decreases toward the externally-threaded portion 3 a (in FIG. 2, in a downward direction). Specifically, the taper surface 3 b is formed to extend from an upper edge to an intermediate position of the collet chuck 3.

The casing 4 is formed in a ring shape, and fitted onto the outer peripheral surface of the collet chuck 3 in a surrounding manner. The casing 4 has an inner peripheral surface formed as a taper surface 4 a in surface contact with the taper surface 3 b formed in the outer peripheral surface of the collet chuck 3. That is, the taper surface 4 a is formed to have a diameter which gradually decreases in the downward direction in conformity to the taper surface 3 b.

The washer 5 is attached onto a bottom surface of the casing 4, and the nut 6 is fastened to the externally-threaded portion 3 a of the collet chuck 3 from below the washer 5. When the nut 6 is fastened (i.e., rotated in a tightening direction), the collet chuck 3 is pulled downwardly, and the taper surface 3 b of the collet chuck 3 is slidingly moved downwardly along the taper surface 4 a of the casing 4. Thus, the collet chuck 3 is reduced in diameter to apply a compressive stress to the shaping member 1 through the pressure-applying member 2.

The shaping tool is designed to satisfy the following relation: A1>A2≈A3≈A4 and A5>A2≈A3≈A4, wherein: A1 is a linear thermal expansion coefficient of the pressure-applying member 2; A2 is a linear thermal expansion coefficient of the collet chuck 3; A3 is a linear thermal expansion coefficient of the casing 4; A4 is a linear thermal expansion coefficient of the nut 6; and A5 is a linear thermal expansion coefficient of the washer 5. This makes it possible to apply a higher compressive stress to the shaping member 1 as a working temperature is increased, as mentioned above.

Second Embodiment

FIG. 4 is a sectional perspective view showing a shaping tool according to a second embodiment of the present invention. The shaping tool illustrated in FIG. 4 has a structure where the washer is omitted from the shaping tool according to the first embodiment. The remaining structure is the same as that in the first embodiment. Therefore, the same element or component as that in the first embodiment is defined by the same reference code, and its description will be omitted.

In the shaping tool according to the second embodiment, a clamping force of a collet chuck 3 can be adjusted to apply a compressive force in the same manner as that in the first embodiment, although a compressive stress based on thermal expansion of the washer cannot be obtained.

Third Embodiment

FIG. 5 is a sectional perspective view showing a shaping tool according to a third embodiment of the present invention. The shaping tool illustrated in FIG. 5 comprises a pressure-applying member 2 which is divided equally into a plurality of sub-members in a circumferential direction thereof, in such a manner that the divided sub-members are disposed in a non-contact relation to each other. The remaining structure is the same as that in the first embodiment. Therefore, the same element or component as that in the first embodiment is defined by the same reference code, and its description will be omitted.

The shaping tool according to the third embodiment has the same function/effect as that in the first embodiment.

Fourth Embodiment

FIG. 6 is a sectional perspective view showing a shaping tool according to a fourth embodiment of the present invention. The shaping tool illustrated in FIG. 6 has a structure where the washer is omitted from the shaping tool according to the third embodiment. The remaining structure is the same as that in the third embodiment. Therefore, the same element or component as that in the third embodiment is defined by the same reference code, and its description will be omitted.

The shaping tool according to the fourth embodiment has the same function/effect as that in the second embodiment.

Fifth Embodiment

FIG. 7 is a sectional perspective view showing a shaping tool according to a fifth embodiment of the present invention. Differently from the aforementioned embodiments using the nut to clamp the collet chuck, the shaping tool according to the fifth embodiment employs a bolt 8 in place of the nut. In FIG. 7, the same element or component as that in the aforementioned embodiments is defined by the same reference code, and its description will be omitted.

Specifically, the shaping tool according to the fifth embodiment comprises a casing 4 which has an internally-threaded portion 4 b in an upper end region of an inner peripheral surface thereof. The bolt 8 has a hexagonal socket, and threadingly fastened to the internally-threaded portion 4 b through a washer 5. The casing 4 has a taper surface 4 a formed in the inner peripheral surface thereof to have a diameter which gradually increases toward the internally-threaded portion 4 b, and the collet chuck 3 has a taper surface 3 b formed in an outer peripheral surface thereof to be in surface contact with the taper surface 4 a of the casing 4.

Thus, when the bolt 8 is threadingly fastened to the internally-threaded portion 4 b of the casing 4 (i.e., rotated in a tightening direction), the collet chuck 3 is pressed downwardly, and the taper surface 3 b of the collet chuck 3 is slidingly moved downwardly along the taper surface 4 a of the casing 4, so that the collet chuck 3 is reduced in diameter to apply a compressive stress to a shaping member 1 through a pressure-applying member 2.

The shaping tool according to the fifth embodiment is designed to satisfy the following relations: A1>A2≈A3≈A6 and A5>A2≈A3≈A6, wherein: A1 is a linear thermal expansion coefficient of the pressure-applying member 2; A2 is a linear thermal expansion coefficient of the collet chuck 3; A3 is a linear thermal expansion coefficient of the casing 4; A6 is a linear thermal expansion coefficient of the bolt 8; and A5 is a linear thermal expansion coefficient of the washer 5. This makes it possible to apply a higher compressive stress to the shaping member 1 as a working temperature is increased, as mentioned above.

Sixth Embodiment

FIG. 8 is a perspective view showing a shaping tool according to a sixth embodiment of the present invention. The shaping tool illustrated in FIG. 8 comprises a shaping member 11, a pressure-applying mechanism section 12 serving as an inner circumferential ring, and an outer circumferential ring 13.

The shaping member 11 is provided with a shaping cavity 11 a on an inward side of an upper end thereof. The pressure-applying mechanism section 12 is formed in a ring shape, and shrinkage-fitted onto an outer peripheral surface of the shaping member 11 in a surrounding manner. Further, the outer circumferential ring 13 is shrinkage-fitted onto an outer peripheral surface of the pressure-applying mechanism section 12. the pressure-applying mechanism section 12 is provided with eight outer peripheral slits 12 a and eight inner peripheral slits 12 b, which are alternately arranged with respect to each other at even intervals in a circumferential direction of the pressure-applying mechanism section 12 (i.e., circumferentially arranged in alternate relation and at even intervals). Each of the outer peripheral slits 12 a is formed to penetrate between a top surface and a bottom surface of the pressure-applying mechanism section 12 and extend radially in such a manner as to be opened only in the outer peripheral surface of the pressure-applying mechanism section 12. Each of the inner peripheral slits 12 b is formed to penetrate between the top surface and the bottom surface of the pressure-applying mechanism section 12 and extend radially in such a manner as to be opened only in an inner peripheral surface of the pressure-applying mechanism section 12.

The pressure-applying mechanism section 12 is made of a material having a linear thermal expansion coefficient greater than that of the outer circumferential ring 13. This makes it possible to apply a higher compressive stress to the shaping member 11 as a working temperature is increased, as mentioned above. More specifically, a pressing temperature is increased by heating the pressure-applying mechanism section 12 using a heater, such as a sheathed heater, inserted thereinto (or embedded therein), or heating the entire shaping tool using an infrared lamp, so as to facilitate a plastic working for a material having low plastic workability, and generate a resistive force enough to cancel out a destructive tensile force imposed on the shaping member 11 due to a plastic working pressure.

Seventh Embodiment

FIG. 9 is a perspective view showing a shaping tool according to a seventh embodiment of the present invention. In the shaping tool illustrated in FIG. 9, a pressure-applying mechanism section 12 is divided into eight sub-members in a circumferential direction thereof, in such a manner that the divided sub-members are disposed in a non-contact relation to each other, and arranged around an outer peripheral surface of the shaping member 11, and an outer circumferential ring 13 is shrinkage-fitted onto an outer peripheral surface of the pressure-applying mechanism section 12 in a surrounding manner. The remaining structure is the same as that in the sixth embodiment. Therefore, the same element or component as that in the sixth embodiment is defined by the same reference code, and its description will be omitted.

The shaping tool according to the seventh embodiment has the same function/effect as that in the sixth embodiment.

The following description will be made about specific examples of the shaping tool according to the first, third, sixth and seventh embodiments.

EXAMPLE 1

As shown in FIG. 10, a molybdenum (Mo) chip having a diameter of 2.5 mm and a length of 3.0 mm was subjected to warm forging using the shaping tool according to the first embodiment to produce a torch-shaped pin so as to evaluate a usable life of the shaping tool. For comparison, the same process was performed using a conventional shaping tool as shown in FIG. 12. This conventional shaping tool is a double shrinkage-fitted type where two ring-shaped members 20, 40 are simply shrinkage-fitted relative to a shaping member 1 in a surrounding manner, wherein a fitting clearance between the shaping member 1 and the ring-shaped member 20 is set at 0.006 mm, and a fitting clearance between the ring-shaped member 20 and the ring-shaped member 40 is set at 0.015 mm. The following description will be made on the assumption that the ring-shaped member 20 and the ring-shaped member 40 correspond, respectively, to the pressure-applying member 2 and the casing 4 in the shaping tool according to the embodiments of the present invention.

In Example 1, the shaping member was made of various hard and brittle materials consisting of HSS, hard metal, cermet, ceramics and diamond. Specifically, a matrix-type HSS [YXR 33 produced by Hitachi Metals, Ltd.: linear thermal expansion coefficient Tc=12.1×10⁻⁶/° C. (20 to 400° C.)] was used as the HSS. A WC—Co based hard metal [G 30 produced by Nippon Tungsten Co., Ltd.: Tc=5.7×10⁻⁶/° C. (20 to 400° C.)] and a WC—Co based ultrafine-grained hard metal [FN-10 produced by Nippon Tungsten Co., Ltd.: Tc=5.1×10⁻⁶/° C. (20 to 400° C.)] were used as the hard metal. A Cr—Mo—Ni—W iron-base complex boride [KH-V60 produced by Toyo Kohan Co., Ltd.: Tc=8.8×10⁻⁶/° C. (20 to 400° C.)] was used as the cermet. A Si₃N₄ sintered material [NPN-3 produced by Nippon Tungsten Co., Ltd.: Tc=3.6×10⁻⁶/° C. (20 to 400° C.)] was used as the ceramics, and a sintered diamond using Co as a binder [Tc=3.1×10⁻⁶/C (20 to 400° C.)] was used as the diamond.

The pressure-applying member for inventive samples was made of tool steel SKD-61 [JIS (Japanese Industrial Standards): linear thermal expansion coefficient A1=12.54×10⁻⁶/° C. (20 to 400° C.)]; Young's modulus Ep=210 GPa]. The pressure-applying member for comparative samples was made of the WC—Co based hard metal [G 30 produced by Nippon Tungsten Co., Ltd.: Tc=5.7×10⁻⁶/° C. (20 to 400° C.)]. The collet chuck was made of an ultra heat-resistant alloy HRA 929 [produced by Hitachi Metals, Ltd.: linear thermal expansion coefficient A2=5.5×10⁻⁶/° C. (at 400° C.) and ≈5.9×10⁻⁶/° C. (at room temperature)]. The casing was made of the WC—Co based hard metal [G 30 produced by Nippon Tungsten Co., Ltd.: linear thermal expansion coefficient A3=5.7×10⁻⁶/° C. (20 to 400° C.)] or a WC—Ni based hard metal [NR-8 produced by Nippon Tungsten Co., Ltd.: A3=5.7×10⁻⁶/° C. (20 to 400° C.)]. The nut was made of the ultra heat-resistant alloy HRA 929 [produced by Hitachi Metals, Ltd.: linear thermal expansion coefficient A4=5.5×10⁻⁶/° C. (at 400° C.) and ≈5.9×10⁻⁶/° C. (at room temperature)]. The washer was made of the SKD61 [JIS: linear thermal expansion coefficient A5=12.54×10⁻⁶/° C. (20 to 400° C.)].

The warm forging was performed using a press machine under the condition that a working temperature was set at 400° C. (by heating the shaping tool using a sheathed heater), and the usable life was evaluated based on the number of shots at a time when the shaping member is fractured, or a wear depth at a forwardly-pressing narrowed edge of the shaping member corresponding to a 45-degree region A (see FIG. 10) of the shaping cavity reaches 0.04 mm. The forwardly-pressing narrowed edge of the shaping cavity was designed to have a curvature radius R of 0.2 mm, and a change in shape of each shaped product at a position corresponding to the narrowed edge was projected by a profile projector, and read to measure the wear depth.

A result of the test is shown in Table 1.

TABLE 1 Pressure-Applying SAMPLE Shaping Member Member Collet Chuck Casing Nut Washer Result Inventive 1 HSS SKD-61 ultra heat-resistant WC—Co ultra heat-resistant SKD-61 about 800 Sample alloy HRA 929 based hard metal alloy HRA 929 shots, due to wear 2 WC—Co SKD-61 ultra heat-resistant WC—Co ultra heat-resistant SKD-61 about 15900 based hard metal alloy HRA 929 based hard metal alloy HRA 929 shots, due to wear 3 WC—Ni SKD-61 ultra heat-resistant WC—Ni ultra heat-resistant SKD-61 about 13800 based hard metal alloy HRA 929 based hard metal alloy HRA 929 shots, due to wear 4 WC—Co SKD-61 ultra heat-resistant WC—Co ultra heat-resistant SKD-61 about 18400 based ultrafine- alloy HRA 929 based hard metal alloy HRA 929 shots, due grained hard metal to wear 5 cermet SKD-61 ultra heat-resistant WC—Co ultra heat-resistant SKD-61 about 22300 alloy HRA 929 based hard metal alloy HRA 929 shots, due to crack 6 ceramics SKD-61 ultra heat-resistant WC—Co ultra heat-resistant SKD-61 about 36400 alloy HRA 929 based hard metal alloy HRA 929 shots, due to crack 7 diamond SKD-61 ultra heat-resistant WC—Co ultra heat-resistant SKD-61 120902 shots, alloy HRA 929 based hard metal alloy HRA 929 due to crack Comparative 8 HSS WC—Co — WC—Co — — 314 shots, Sample based hard metal based hard metal due to crack 9 WC—Co WC—Co — WC—Co — — 1 shot, due based hard metal based hard metal based hard metal to fracture 10 cermet WC—Co — WC—Co — — 1 shot, due based hard metal based hard metal to fracture 11 ceramics WC—Co — WC—Co — — 1 shot, due based hard metal based hard metal to fracture

As seen in Table 1, the present invention could provide a shaping tool having high wear resistance and fracture resistance to achieve an extended usable life.

In contrast, the conventional shaping tool (comparative samples) could not resist to a tensile stress imposed on the shaping tool due to a working pressure during the warm forging, and failed to obtain a practically usable life due to fracture occurring within a short period of time.

EXAMPLE 2

Based on the shaping tool according to the third embodiment, a test was carried out in the same manner as that in the Example 1. The components of the shaping tool were also made in the same manner as those in the Example 1.

A result of the test is shown in Table 2.

TABLE 2 Pressure-Applying SAMPLE Shaping Member Member Collet Chuck Casing Nut Washer Result Inventive 1 HSS SKD-61 ultra heat-resistant WC—Co ultra heat-resistant SKD-61 about 700 Sample alloy HRA 929 based hard metal alloy HRA 929 shots, due to wear 2 WC—Co SKD-61 ultra heat-resistant WC—Co ultra heat-resistant SKD-61 about 15200 based hard metal alloy HRA 929 based hard metal alloy HRA 929 shots, due to wear 3 WC—Ni SKD-61 ultra heat-resistant WC—Ni ultra heat-resistant SKD-61 about 14600 based hard metal alloy HRA 929 based hard metal alloy HRA 929 shots, due to wear 4 WC—Co SKD-61 ultra heat-resistant WC—Co ultra heat-resistant SKD-61 about 19000 based ultrafine- alloy HRA 929 based hard metal alloy HRA 929 shots, due grained hard metal to wear 5 cermet SKD-61 ultra heat-resistant WC—Co ultra heat-resistant SKD-61 about 22100 alloy HRA 929 based hard metal alloy HRA 929 shots, due to crack 6 ceramics SKD-61 ultra heat-resistant WC—Co ultra heat-resistant SKD-61 about 37200 alloy HRA 929 based hard metal alloy HRA 929 shots, due to crack 7 diamond SKD-61 ultra heat-resistant WC—Co ultra heat-resistant SKD-61 128580 alloy HRA 929 based hard metal alloy HRA 929 shots, due to crack Comparative 8 HSS WC—Co — WC—Co — — 314 shots, Sample based hard metal based hard metal due to crack 9 WC—Co WC—Co — WC—Co — — 1 shot, due based hard metal based hard metal based hard metal to fracture 10 cermet WC—Co — WC—Co — — 1 shot, due based hard metal based hard metal to fracture 11 ceramics WC—Co — WC—Co — — 1 shot, due based hard metal based hard metal to fracture

As seen in Table 2, the present invention could provide a shaping tool having high wear resistance and fracture resistance to achieve an extended usable life.

EXAMPLE 3

Under the same conditions as those in the Example 1, the warm forging was performed while increasing a working temperature up to about 200 to 800° C. by attaching or inserting a heater, such as a directly-attachable type, onto/into the collet chuck or by irradiating the entire shaping tool with infrared light or the like. As a result, a worm forging for a material having low plastic workability was facilitated, and a pressing speed was increased. In addition, a compressive stress could be applied to the shaping member at a value about 1.2 to 1.5 times greater than that in the Example 1. Thus, even when a high working pressure was imposed on the shaping member during a plastic working for a material having low plastic workability, such as tungsten (W), the shaping tool could avoid fracture to achieve a usable life equivalent to that in a plastic working for Mo having higher plastic workability than that of W.

EXAMPLE 4

As shown in FIG. 11, a Mo chip having a diameter of 2.2 mm and a length of 2.4 mm was subjected to warm press using the shaping tool according to the sixth embodiment to produce a torch-shaped pin so as to evaluate a usable life of the shaping tool. The press working was carried out while heating the pressure-applying mechanism section 12 up to about 400° C. using a sheathed heater embedded therein. For comparison, the aforementioned conventional shaping tool illustrated in FIG. 12 was used. The following description will be made on the assumption that the ring-shaped member 20 and the ring-shaped member 40 correspond, respectively, to the pressure-applying mechanism section 12 and the outer circumferential ring 13 in the shaping tool according to the embodiments of the present invention.

In Example 4, the shaping member was made of various hard and brittle materials consisting of HSS, hard metal, cermet, ceramics and diamond. Specifically, a matrix-type HSS [YXR 33 produced by Hitachi Metals, Ltd.: linear thermal expansion coefficient Tc=12.1×10⁻⁶/° C. (200 to 400° C.)] was used as the HSS. A WC—Co based hard metal [G 30 produced by Nippon Tungsten Co., Ltd.: Tc=5.7×10⁻⁶/° C. (20 to 400° C.)] and a WC—Co based ultrafine-grained hard metal [FN-10 produced by Nippon Tungsten Co., Ltd.: Tc=5.1×10⁻⁶/° C. (20 to 400° C.)] were used as the hard metal. A Cr—Mo—Ni—W iron-base complex boride [KH-V60 produced by Toyo Kohan Co., Ltd.: Tc=8.8×10⁻⁶/° C. (20 to 400° C.)] was used as the cermet. A Si₃N₄ sintered material [NPN-3 produced by Nippon Tungsten Co., Ltd.: Tc=3.6×10⁻⁶/C (20 to 400° C.)] was used as the ceramics, and a sintered diamond using Co as a binder [Tc=3.1×10⁻⁶/° C. (20 to 400° C.)] was used as the diamond. The pressure-applying mechanism section (inner circumferential ring) was made of tool steel SKD-61 [JIS (Japanese Industrial Standards): Tc=12.54×10⁻⁶/° C. (20 to 400° C.)]; Young's modulus Ep=210 GPa]. The outer circumferential ring was made of the WC—Co based hard metal [G 30 produced by Nippon Tungsten Co., Ltd.: Tc=5.7×10⁻⁶/° C. (20 to 400° C.); Young's modulus Ep=550 GPa] or a WC—Ni based hard metal [NR-8 produced by Nippon Tungsten Co., Ltd.: Tc=5.7×10⁻⁶/° C. (20 to 400° C.); Young's modulus Ep=530 GPa].

A result of the test is shown in Table 3.

The usable life was evaluated based on the number of shots at a time when the shaping member is fractured, or a wear depth at a forwardly-pressing narrowed edge of the shaping member corresponding to a 45-degree region B (see FIG. 11) of the shaping cavity reaches 0.04 mm. The forwardly-pressing narrowed edge of the shaping cavity was designed to have a curvature radius R of 0.2 mm, and a change in shape of each shaped product at a position corresponding to the narrowed edge was projected by a profile projector, and read to measure the wear depth.

TABLE 3 Pressure-Applying Outer Circumferential SAMPLE Shaping Member Mechanism Section Ring Result Inventive 1 HSS SKD-61 WC—Co based hard metal about 800 shots, due to wear Sample 2 HSS SKD-61 WC—Ni based hard metal about 800 shots, due to wear 3 WC—Co based hard metal SKD-61 WC—Co based hard metal about 12800 shots, due to wear 4 WC—Co based ultrafine- SKD-61 WC—Ni based hard metal about 15400 shots, due to wear grained hard metal 5 cermet SKD-61 WC—Co based hard metal about 18300 shots, due to crack 6 cermet SKD-61 WC—Ni based hard metal about 18300 shots, due to crack 7 ceramics SKD-61 WC—Co based hard metal about 19000 shots, due to crack 8 ceramics SKD-61 WC—Ni based hard metal about 19000 shots, due to crack 9 diamond SKD-61 WC—Co based hard metal about 11000000 shots, due to crack 10 diamond SKD-61 WC—Ni based hard metal about 11000000 shots, due to crack Comparative 11 HSS SKD-61 WC—Co based hard metal about 500 shots, due to crack Sample 12 hard metal SKD-61 WC—Co based hard metal 1 shot, due to fracture 13 cermet SKD-61 WC—Co based hard metal 1 shot, due to fracture 14 ceramics SKD-61 WC—Co based hard metal 1 shot, due to fracture 15 diamond SKD-61 WC—Co based hard metal 1 shot, due to fracture

As seen in Table 3, the present invention could provide a shaping tool having high wear resistance and fracture resistance to achieve an extended usable life.

For the inventive samples in Table 3, the shaping member was made of each of the hard and brittle materials consisting of the matrix-type HSS, the WC—Co based hard metal, the WC—Co based ultrafine-grained hard metal, the Cr—Mo—Ni—W iron-base complex boride, the sintered material, and the sintered diamond using Co as a binder. Further, the pressure-applying mechanism section (inner circumferential ring) was made of the tool steel SKD-61, and the outer circumferential ring was made of each of the WC—Co based hard metal and the WC—Ni based hard metal. In an additional test using each of different HSS, hard metal, cermet, ceramics and diamond, the same result could be obtained.

In contrast, the conventional shaping tool (comparative samples) could not resist to a tensile stress imposed on the shaping tool due to a working pressure during the press working, and failed to obtain a practically usable life due to fracture occurring within a short period of time.

EXAMPLE 5

Under the same conditions as those in the Example 4, the press working was performed while increasing a working temperature up to about 600° C. by inserting a heater, such as a sheathed heater, into the pressure-applying mechanism section or by irradiating the entire shaping tool using an infrared lamp or the like. That is, the press working was carried out at a temperature greater than that in Example 4 by about 200° C. As a result, a plastic working for a material having low plastic workability was facilitated. In addition, a resistive force for cancelling out a destructive tensile force imposed on the shaping member due to a working pressure generated during the plastic working could be increased as compared with the Example 4, so as to facilitate the press working and increase a pressing speed. Specifically, a compressive stress was applied to the shaping member at a value about 1.2 to 1.5 times greater than that in the Example 4. Thus, even when a high working pressure was imposed on the shaping member during a plastic working for a material having low plastic workability, such as W, the shaping tool could avoid fracture to achieve a usable life equivalent to that in a plastic working for Mo having higher plastic workability than that of W.

EXAMPLE 6

Under the same conditions as those in the Example 4, the pressure-applying mechanism section and the outer circumferential ring were made of a WC—Co based hard metal, and formed to have the same linear thermal expansion coefficient, to perform a press working. The shaping member is typically made of a hard and brittle material, as mentioned above. Therefore, the shaping member has a linear thermal expansion coefficient less than that of the pressure-applying mechanism section and the outer circumferential ring, and thereby a compressive stress can be applied to the shaping member. Thus, even if a working pressure was increased to impose a tensile stress on the shaping member, a compressive stress enough to cancel out the tensile stress could be applied to the shaping member so as to prevent fracture of the shaping member. Further, not only Mo but also a material having low plastic workability, such as W, could be desirably subjected to plastic working by heating the shaping tool up to a ductile-brittle transition temperature or more.

EXAMPLE 7

Based on the shaping tool according to the seventh embodiment, a test was carried out in the same manner as that in the Example 4. The components of the shaping tool were also made in the same manner as those in the Example 4.

A result of the test is shown in Table 4.

TABLE 4 Pressure-Applying Outer Circumferential SAMPLE Shaping Member Mechanism Section Ring Result Inventive 1 HSS SKD-61 WC—Co based hard metal about 800 shots, due to wear Sample 2 HSS SKD-61 WC—Ni based hard metal about 800 shots, due to wear 3 WC—Co based hard metal SKD-61 WC—Co based hard metal about 12800 shots, due to wear 4 WC—Co based ultrafine- SKD-61 WC—Ni based hard metal about 15400 shots, due to wear grained hard metal 5 cermet SKD-61 WC—Co based hard metal about 18300 shots, due to crack 6 cermet SKD-61 WC—Ni based hard metal about 18300 shots, due to crack 7 ceramics SKD-61 WC—Co based hard metal about 19000 shots, due to crack 8 ceramics SKD-61 WC—Ni based hard metal about 19000 shots, due to crack 9 diamond SKD-61 WC—Co based hard metal about 11000000 shots, due to crack 10 diamond SKD-61 WC—Ni based hard metal about 11000000 shots, due to crack Comparative 11 HSS SKD-61 WC—Co based hard metal about 500 shots, due to crack Sample 12 hard metal SKD-61 WC—Co based hard metal 1 shot, due to fracture 13 cermet SKD-61 WC—Co based hard metal 1 shot, due to fracture 14 ceramics SKD-61 WC—Co based hard metal 1 shot, due to fracture 15 diamond SKD-61 WC—Co based hard metal 1 shot, due to fracture

As seen in Table 4, the present invention could provide a shaping tool having high wear resistance and fracture resistance to achieve an extended usable life.

For the inventive samples in Table 4, the shaping member was made of each of the hard and brittle materials consisting of the matrix-type HSS, the WC—Co based hard metal, the WC—Co based ultrafine-grained hard metal, the Cr—Mo—Ni—W iron-base complex boride, the Si₃N₄ sintered material, and the sintered diamond using Co as a binder. Further, the pressure-applying mechanism section (inner circumferential ring) was made of the tool steel SKD-61, and the outer circumferential ring was made of each of the WC—Co based hard metal and the WC—Ni based hard metal. In an additional test using each of different HSS, hard metal, cermet, ceramics and diamond, the same result could be obtained.

In contrast, the conventional shaping tool (comparative samples) could not resist to a tensile stress imposed on the shaping tool due to a working pressure during the press working, and failed to obtain a practically usable life due to fracture occurring within a short period of time.

EXAMPLE 8

Under the same conditions as those in the Example 7, the press working was performed while increasing a working temperature up to about 600° C. by inserting a heater, such as a sheathed heater, into the pressure-applying mechanism section or by irradiating the entire shaping tool using an infrared lamp or the like. That is, the press working was carried out at a temperature greater than that in Example 6 by about 200° C. As a result, a plastic working for a material having low plastic workability was facilitated. In addition, a resistive force for cancelling out a destructive tensile force imposed on the shaping member due to a working pressure generated during the plastic working could be increased as compared with the Example 6, so as to facilitate the press working and increase a pressing speed. Specifically, a compressive stress was applied to the shaping member at a value about 1.2 to 1.5 times greater than that in the Example 6. Thus, even when a high working pressure was imposed on the shaping member during a plastic working for a material having low plastic workability, such as W, the shaping tool could avoid fracture to achieve a usable life equivalent to that in a plastic working for Mo having higher plastic workability than that of W.

EXAMPLE 9

Under the same conditions as those in the Example 7, the pressure-applying mechanism section and the outer circumferential ring were made of a WC—Co based hard metal, and formed to have the same linear thermal expansion coefficient, to perform a press working. The shaping member is typically made of a hard and brittle material, as mentioned above. Therefore, the shaping member has a linear thermal expansion coefficient less than that of the pressure-applying mechanism section and the outer circumferential ring, and thereby a compressive stress can be applied to the shaping member. Thus, even if a working pressure was increased to impose a tensile stress on the shaping member, a compressive stress enough to cancel out the tensile stress could be applied to the shaping member so as to prevent fracture of the shaping member. Further, not only Mo but also a material having low plastic workability, such as W, could be desirably subjected to plastic working by heating the shaping tool up to a ductile-brittle transition temperature or more.

INDUSTRIAL APPLICABILITY

The shaping tool of the present invention can be formed in a specific shape to obtain a shaped product having an intended shape even if a material is a metal having a high melting point and low plastic workability, such as Mo, W, Ta or Nb. Thus, the present invention can be used, for example, in producing an electrode for discharge lamps. Further, in the shaping tool of the present invention, a larger compressive stress is applied to the shaping member as a working temperature is increased. Thus, the shaping tool of the present invention is suited, particularly, to working for a metal which has a high melting point and low plastic workability, such as Mo, W, Ta or Nb, and thereby requires a high working pressure.

The present invention can also be applicable to a tool (e.g., a precision chuck for a rotating tool, such as an end mill) requiring high dimensional accuracy, strong clamping force and high wear resistance in a clamping portion.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded perspective view showing a shaping tool according to a first embodiment of the present invention.

FIG. 2 is a sectional perspective view showing the shaping tool illustrated in FIG. 1 which is in an assembled state.

FIG. 3 is a top plan view of a pressure-applying member which is one component of the shaping tool.

FIG. 4 is a sectional perspective view showing a shaping tool according to a second embodiment of the present invention.

FIG. 5 is a sectional perspective view showing a shaping tool according to a third embodiment of the present invention.

FIG. 6 is a sectional perspective view showing a shaping tool according to a fourth embodiment of the present invention.

FIG. 7 is a sectional perspective view showing a shaping tool according to a fifth embodiment of the present invention.

FIG. 8 is a perspective view showing a shaping tool according to a sixth embodiment of the present invention.

FIG. 9 is a perspective view showing a shaping tool according to a seventh embodiment of the present invention.

FIG. 10 illustrates a change in shape of a shaped product during warm-forging working.

FIG. 11 illustrates a change in shape of a shaped product during press working.

FIG. 12 is a sectional perspective view showing a conventional shaping tool.

EXPLANATION OF CODES

-   -   1, 11: shaping member     -   1 a, 11 a: shaping cavity     -   2: pressure-applying member     -   2 a: outer peripheral slit     -   2 b: inner peripheral slit     -   3: collet chuck     -   3 a: externally-threaded portion     -   3 b: taper surface     -   4: casing     -   4 a: taper surface     -   4 b: internally-threaded portion     -   5: washer     -   6: nut     -   7: shim     -   8: bolt     -   12: pressure-applying mechanism section     -   12 a: outer peripheral slit     -   12 b: inner peripheral slit     -   13: outer circumferential ring     -   20, 40: ring-shaped member 

1. A shaping tool comprising: a columnar-shaped shaping member having a shaping cavity on an inward side thereof; a ring-shaped pressure-applying member fitted onto an outer peripheral surface of said shaping member in a surrounding manner; a ring-shaped collet chuck fitted onto an outer peripheral surface of said pressure-applying member in a surrounding manner; and a ring-shaped casing fitted onto an outer peripheral surface of said collet chuck in a surrounding manner, said shaping tool being characterized in that: said pressure-applying member has a plurality of outer peripheral slits and a plurality of inner peripheral slits, each of said outer peripheral slits being formed to penetrate between a top surface and a bottom surface of said pressure-applying member and extend radially in such a manner as to be opened in the outer peripheral surface of said pressure-applying member, each of said inner peripheral slits being formed to penetrate between the top surface and the bottom surface of said pressure-applying member and extend radially in such a manner as to be opened in an inner peripheral surface of said pressure-applying member, said outer peripheral slits being alternately arranged with respect to said inner peripheral slits along a circumferential direction of said pressure-applying member; said collet chuck has an externally-threaded portion at an upper or lower end thereof, and a taper surface formed in the outer peripheral surface thereof to have a diameter which gradually decreases toward said externally-threaded portion; and said casing has an inner peripheral surface formed as a taper surface in surface contact with said taper surface formed in the outer peripheral surface of said collet chuck, wherein: said shaping tool includes a nut disposed above or below said casing; and said collet chuck is adapted to be reduced in diameter by fastening said nut to said externally-threaded portion of said collet chuck.
 2. A shaping tool comprising: a columnar-shaped shaping member having a shaping cavity on an inward side thereof; a ring-shaped pressure-applying member fitted onto an outer peripheral surface of said shaping member in a surrounding manner; a ring-shaped collet chuck fitted onto an outer peripheral surface of said pressure-applying member in a surrounding manner; and a ring-shaped casing fitted onto an outer peripheral surface of said collet chuck in a surrounding manner, said shaping tool being characterized in that: said pressure-applying member is divided into a plurality of sub-members in a circumferential direction thereof, in such a manner that said sub-members are disposed in a non-contact relation to each other; said collet chuck has an externally-threaded portion at an upper or lower end thereof, and a taper surface formed in the outer peripheral surface thereof to have a diameter which gradually decreases toward said externally-threaded portion; and said casing has an inner peripheral surface formed as a taper surface in surface contact with said taper surface formed in the outer peripheral surface of said collet chuck, wherein: said shaping tool includes a nut disposed above or below said casing; and said collet chuck is adapted to be reduced in diameter by fastening said nut to said externally-threaded portion of said collet chuck.
 3. The shaping tool as defined in claim 1 or 2, which is designed to satisfy the following relation: A1>A2≈A3≈A4 , wherein: A1 is a linear thermal expansion coefficient of said pressure-applying member; A2 is a linear thermal expansion coefficient of said collet chuck; A3 is a linear thermal expansion coefficient of said casing; and A4 is a linear thermal expansion coefficient of said nut.
 4. The shaping tool as defined in any one of claims 1 or 2, wherein said nut is disposed above or below said casing while interposing a washer therebetween, wherein said shaping tool is designed to satisfy the following relation: A5>A2≈A3≈A4 , wherein: A2 is a linear thermal expansion coefficient of said collet chuck; A3 is a linear thermal expansion coefficient of said casing; A4 is a linear thermal expansion coefficient of said nut; and A5 is a linear thermal expansion coefficient of said washer.
 5. A shaping tool comprising: a columnar-shaped shaping member having a shaping cavity on an inward side thereof; a ring-shaped pressure-applying member fitted onto an outer peripheral surface of said shaping member in a surrounding manner; a ring-shaped collet chuck fitted onto an outer peripheral surface of said pressure-applying member in a surrounding manner; and a ring-shaped casing fitted onto an outer peripheral surface of said collet chuck in a surrounding manner, said shaping tool being characterized in that: said pressure-applying member has a plurality of outer peripheral slits and a plurality of inner peripheral slits, each of said outer peripheral slits being formed to penetrate between a top surface and a bottom surface of said pressure-applying member and extend radially in such a manner as to be opened in the outer peripheral surface of said pressure-applying member, each of said inner peripheral slits being formed to penetrate between the top surface and the bottom surface of said pressure-applying member and extend radially in such a manner as to be opened in an inner peripheral surface of said pressure-applying member, said outer peripheral slits being alternately arranged with respect to said inner peripheral slits along a circumferential direction of said pressure-applying member; said casing has an internally-threaded portion in an upper or lower end region of an inner peripheral surface thereof, and a taper surface formed in the inner peripheral surface thereof to have a diameter which gradually increases toward said internally-threaded portion; and said collet chuck has a taper surface formed in the outer peripheral surface thereof to be in surface contact with said taper surface formed in the inner peripheral surface of said casing, wherein: said shaping tool includes a bolt which is disposed above or below said collet chuck; and said collet chuck is adapted to be reduced in diameter by fastening said bolt to said internally-threaded portion of said casing.
 6. A shaping tool comprising: a columnar-shaped shaping member having a shaping cavity on an inward side thereof; a ring-shaped pressure-applying member fitted onto an outer peripheral surface of said shaping member in a surrounding manner; a ring-shaped collet chuck fitted onto an outer peripheral surface of said pressure-applying member in a surrounding manner; and a ring-shaped casing fitted onto an outer peripheral surface of said collet chuck in a surrounding manner, said shaping tool being characterized in that: said pressure-applying member is divided into a plurality of sub-members in a circumferential direction thereof, in such a manner that said sub-members are disposed in a non-contact relation to each other; said casing has an internally-threaded portion in an upper or lower end region of an inner peripheral surface thereof, and a taper surface formed in the inner peripheral surface thereof to have a diameter which gradually increases toward said internally-threaded portion; and said collet chuck has a taper surface formed in the outer peripheral surface thereof to be in surface contact with said taper surface formed in the inner peripheral surface of said casing, wherein: said shaping tool includes a bolt which is disposed above or below said collet chuck; and said collet chuck is adapted to be reduced in diameter by fastening said bolt to said internally-threaded portion of said casing.
 7. The shaping tool as defined in claim 5 or 6, which is designed to satisfy the following relation: A1>A2≈A3≈A6 , wherein: A1 is a linear thermal expansion coefficient of said pressure-applying member; A2 is a linear thermal expansion coefficient of said collet chuck; A3 is a linear thermal expansion coefficient of said casing; and A6 is a linear thermal expansion coefficient of said bolt.
 8. The shaping tool as defined in any one of claims 5 or 6, wherein said bolt is disposed above or below said collet chuck while interposing a washer therebetween, wherein said shaping tool is designed to satisfy the following relation: A5>A2≈A3≈A6 , wherein: A2 is a linear thermal expansion coefficient of said collet chuck; A3 is a linear thermal expansion coefficient of said casing; A6 is a linear thermal expansion coefficient of said bolt; and A5 is a linear thermal expansion coefficient of said washer.
 9. The shaping tool as defined in any one of claims 1, 2, 5 or 6, where said casing has a Young's modulus of 200 GPa or more.
 10. The shaping tool as defined in any one of claims 1, 2, 5 or 6, where said collet chuck has a Young's modulus of 300 GPa or less.
 11. A shaping tool comprising: a columnar-shaped shaping member having a shaping cavity on an inward side thereof; an inner circumferential ring fitted onto an outer peripheral surface of said shaping member in a surrounding manner; and an outer circumferential ring fitted onto an outer peripheral surface of said inner circumferential ring in a surrounding manner, said shaping tool being characterized in that said inner circumferential ring is formed as a pressure-applying mechanism section.
 12. The shaping tool as defined in claim 11, wherein said pressure-applying mechanism section has a structure with a plurality of outer peripheral slits and a plurality of inner peripheral slits, each of said outer peripheral slits being formed to penetrate between a top surface and a bottom surface of said inner circumferential ring and extend radially in such a manner as to be opened in the outer peripheral surface of said inner circumferential ring, each of said inner peripheral slits being formed to penetrate between the top surface and the bottom surface of said inner circumferential ring and extend radially in such a manner as to be opened in an inner peripheral surface of said inner circumferential ring, said outer peripheral slits being alternately arranged with respect to said inner peripheral slits along a circumferential direction of said inner circumferential ring.
 13. The shaping tool as defined in claim 11, wherein said pressure-applying mechanism section has a structure in which said inner circumferential ring is divided into a plurality of sub-members in a circumferential direction thereof, in such a manner that said sub-members are disposed in a non-contact relation to each other.
 14. The shaping tool as defined in any one of claims 11 to 13, wherein said pressure-applying mechanism section has a linear thermal expansion coefficient equal to or greater than that of said outer circumferential ring.
 15. The shaping tool as defined in any one of claims 11 to 13, where said outer circumferential ring has a Young's modulus of 200 GPa or more.
 16. The shaping tool as defined in any one of claims 1, 2, 5, 6 or 11, where said shaping member is made of a hard and brittle material.
 17. The shaping tool as defined in claim 16, wherein said hard and brittle material is at least one selected from the group consisting of high-speed steel (HSS), hard metal, cermet, ceramics and diamond.
 18. A shaping method using the shaping tool as defined in any one of claims 1, 2, 5, 6 or 11, wherein said shaping tool is used at a temperature greater than room temperature.
 19. The method as defined in claim 18, wherein said shaping tool is used in subjecting a metal to plastic working. 